I did a trip similar to the first half of yours last August and I loved it. My route was more like this:
Unfortunatly I lost the first few days tracks but I did something similar to your plan, except I bypassed Zagreb and went straight to the coast of Croatia. I think you are going to miss out by not looping into Bosnia Herzegovina. The city of Mostar and the national parks in the South-eastern part were some of my favorite things from the trip. I highly recommend them. I also recommend that when you swing thru near Villach, Austria you make a stop for coffee in a place called Lake Bled. It is just over the border into Slovenia. It is worth the slight detour, that place is amazing. If you stop for coffee, you will probably stay longer.
As far as crime goes, I did not feel like I was being targeted at all. I spent a month in the Balkans and I had no issues with that. That does not mean I was not weary of crime. It was typically easy to find a secure garage or atleast fenced off low visibility area to park my bike for the night. For the most part I experienced a ton of hospitality everywhere I went.
Follow the signs to the Sobu/Soba/Apartmani. They are rooms that the locals rent out of their homes. They are typically very comfortable, clean, and cheap. Sometimes they even included meals.
I have been to every country on your route, with the exception of Greece, and my German green card insurance was accepted with no problem. On your green card it will indicate all the countries it is accepted in on the bottom.
The road conditions in Albania and Romania can be a bit sketchy at times with many potholes and even main roads consist of long gravel sectons, but certainly passable. Bulgaria's roads have a few issues as well. I cannot say about Greece's. The rest of the countries roads are reasonably well maintained though. Your biggest problem will be the aggressiveness of the drivers. Albania definitely takes the cake in this category. I was forced off the road multiple times when on coming traffic attempted to pass traffic in their lane by coming into mine and simple disregarding my presence. You will see that most motorcycles and scooters in this country ride in the furthest outside 6 inches of tarmac.
I did not notice very much in the way of scams. In fact, nothing comes to mind at all.
That looks like a really great trip and I am sure you will enjoy it. Although, if you get the chance, it seems like your path was created with the intent to cover as much ground as possible in the shortest amount of time. There are a lot of amazing places you will miss. Some of my top cities in that area are Plovdiv, Bulgaria; Brasov, Romania; Pilsen, Czech Republic; Rothenburg ob der Tauber, Germany; Hvar, Croatia; Ston and Moli Ston, Croatia; and Lake Ohrid, Macedonia. Most of those places are just outside your primary path and would be a shame to miss.